The present invention relates generally to improvements in techniques for regulating the feed of steam to a steamer. Such devices are used with respect to the treatment by liquid and steam of continuously passing webs of material, and are frequently used in textile finishing.
If the web material arrives at the steamer after continuous passage through several treatment stations, it will have a total moisture content that is the sum of a number of prior steps that have added moisture to the web. For example, these prior steps can include, the residual moisture remaining after prewashing (after squeezing) and of the amount of moisture added from different impregnation and dyeing or printing processes in each of the subsequent stations. Regardless of the origin of the moisture, the material web must be brought to the steamer temperature with this total load of web moisture. The amount of heat necessary to accomplish this is supplied by the steam introduced into the steamer.
From Federal Republic of Germany Patent 27 16 264, a steamer is known which has downwardly open shafts on the steamer housing for the introduction and removal of the web of material. Within the shafts, a boundary layer is formed between the steam atmosphere prevailing in the steamer housing and the outer air. The position of this boundary layer is determined by means of temperature sensors arranged in the vertical shafts, the signal of which sensors serves to control the feeding of steam into the steamer housing. In this way it is possible to keep the steamer filled with steam without certain amounts of steam continuously flowing off over the lower edge of the vertical shafts and being lost. The amount of steam added can rather be so regulated that the boundary layer remains somewhere in the height of the vertical shafts but does not advance to its lower edge.
The control of the feeding of steam in this manner has the disadvantage of considerable inertia, leading to low starting-up processes until steady conditions are reached. There remains a need for the further development of a method and a system for the treatment of webs of textile material by liquid and steam through which steady-state conditions are established more rapidly.